Impact wrench



E. R. WHITLEDG E IMPACT WRENCH April 28, 1953 4 Sheets-Sheet 1 Filed March 31, 1948 zaydrzzmzyzez 0,

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' IMPACT WRENCH Filed March 31, 1948 4 Shee't's -S heet 4 "Hu MIIIIII\\\\\ INVENTOR. Edgar '22 Wz'z 2842 922,

Patented Apr. 28, 1953 IMPACT WRENCH Edgar R. Whitledge, Mantua, Ohio, assignor to The Aro Equipment Corporation, Bryan, Ohio, a. corporation of Ohio Application March 31, 1948, Serial No. 18,213

'7 Claims.

This invention relates to an impact tool or wrench. The tool is particularly adapted for use as a nut runner and tightener, although the principles involved are not limited thereto.

It is an object of the invention to provide a light, portable impact tool which delivers exceptional power.

It is also an object of the invention to provide an impact tool which is extremely rugged and not subject to breakage.

It is a further object of the invention to provide an impact tool which has a small number of parts.

It is an additional object of the invention to provide an impact wrench which will smoothly turn nuts and the like below a predetermined resistance to torque, and which delivers strong impact blows when a higher resistance to torque is encountered.

It is also an object of the invention to provide an impact tool which delivers an impact blow each time the hammer, or carrier therefor, rotates 360-also, to provide two hammers and impact surfaces which simultaneously engage and disengage after each 360 of rotation.

It is an important object of the invention to dispense with any positive declutching means in an impact tool, such as springs, cams and the like, and to depend entirely on the coaction and shape of the hammer and the impact receiving surfaces to effect declutching.

It is a further object of the invention to provide an impact tool in which the hammers, when rotated, never come to a full stop in an orbital direction, even when an impact blow is delivered.

It is an additional object of the invention to dispense with trackways which have heretofore been provided and over which the hammers roll or slide during rotation, thus reducing friction.

It is another object of the invention to provide an impact tool in which the hammers may be of a variety of easily manufactured shapes.

It is also an object of the invention to provide cushioning for the hammers of an impact tool during the inward movement of the hammers in their carrier.

With these and other objects in view, the invention consists in the construction, arrangement and combination of the various parts of my device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in the claims and illustrated in the accompanying drawings, wherein:

Figure 1 is a partial vertical sectional view of one preferred embodiment of the impact tool;

Figure 2 is a sectional view of the impact tool taken on line 2-2 of Figure 1 and showing the position of the parts at the moment of impact;

Figure 3 is a sectional view similar to Figure 2 showing the position of the parts just after impact;

Figure 4 is a sectional view similar to Figure 2 showing the position of the parts after the hammers have passed the impact abutments;

Figure v5 is a vertical sectional view taken on line 55 of Figure 3;

Figure 6 is a horizontal sectional view of the impact tool taken on line 6-6 of Figure 5;

Figure 7 is a perspective view of the anvil member;

Figure 8 is an exploded perspective view of the hammer carrier and hammers;

Figure 9 is a vertical sectional view of an impact tool illustrating a second embodiment of the invention;

Figure 10 is a sectional view of the impact tool shown in Figure 9, taken on line Ill-iii thereof;

Figure 11 is a vertical sectional view of an impact tool illustrating a third embodiment of the invention;

Figure 12 is a sectional view of the impact tool shown in Figure 11 taken on line l2-l2 thereof; I

Figure 13 is a vertical sectional view of a fourth embodiment of the invention;

Figure 14 is a sectional view taken on line I l-l4 of Figure 13;

Figure 15 is a vertical sectional view embodiment of the invention; and l Figure 16. is a sectional view taken on line IBI6 of Figure 15.

Referring specifically to Figures 1 to 8, inclusive, of the drawings for a detailed description of the first embodiment of the invention, numeral of a fifth 2! designates generally a cup-shaped casing having an opening 22 in the bottom thereof, through which a socket wrench member 23 extends. The other end of the cup-shaped casing is provided with threads 24 for attachment to a suitable motor (not shown) for driving the impact tool. The motor drives a shaft 25, which is provided with bearings 26. The shaft 25 enters a recess 2c in a generally cylindrical hammer carrier member indicated at 21. A driving connection in the form of a square or hexagonal stud is provided on the end of the shaft 25 and engages in the recess 20. The other end of the carrier member 21 is provided with a stud or projection 3| which extends into a recess 32 of an anvil member generally indicated at 33.

The anvil member 33 is of cup shape, and the socket wrench member 23 is either integral therewith, as shown at 36, or is secured thereto by any well known detachable connection. The anvil member is provided with two abutments 3t and 35, each having two impact receiving surfaces 30. The angle of the impact receiving surfaces 39, with respect to a line drawn through the center of abutments 31; and 35, is, for example, 40, although other angles of plus or minus 1 may be utilized. Abutments 34 and 33 are diametrically 180 apart and are offset coaxially of the anvil member 33, as best shown in Figures 1 and 5.

Two circular holes or passages 31 and 38 are provided in the hammer carrier member, as shown, for example, in Figure 8. The holes are coaxial with each other and extend completely through the carrier member. Disposed within the holes 31 and 38 are generally cylindrical hammers, indicated by the numeral 39. The hammers are provided at one end thereof with a slightly curved top 49 and oppositely inclined impact surfaces 4!. The angle of the inclined surfaces 4|, with respect to the center line of the hammers 39, is 16.5 in the preferred form. This angle may vary plus 3.5 and minus 1. The hammers 39 are also provided with undercut portions 42, which are in the shape of one-half an ellipse.

Two pins 43 extend coaxially of the hammer carrier 21 and are inserted in bores 46, as best shown in Figure 6. The bores B11 extend from the end of the hammer carrier 21 adjacent the projection 31, but do not extend completely through the hammer carrier 21.

The unit is assembled by first placing the hammers 39 within the holes 31 and 38 in the hammer carrier 21 with the ends provided with the impacting surfaces 4] extending in opposite directions. The hammers 39 are, therefore, coaxially aligned. The undercuts 42 in the hammers 39 are then aligned and axially spaced from each other so that the pins -43 may be inserted in the bores 44 and be positioned in the undercuts, as best shown in Figures 2, 3 and 4. The hammer carrier 21, with the hammer 29 therein, is then inserted into the anvil 33 with the pilot pin 3i entering the recess 32. This entire assembly is then inserted into the casing 2|, and the end of the shaft 25, which is connected to a motor (not shown), is then disposed in recess 29. Preferably, the motor utilized is a pneumatic motor, although the invention is not limited thereto.

Operation of Figures 1 to 8 When a nut is to be tightened, the socket 33 is placed over the nut and the motor for driving the shaft 25 is rotated. The centrifugal force, due to rotation of the shaft 215 and hammer carrier 21, will almost immediately throw the hammers 39 outwardly and, as the hammer carrier 21 rotates, the impact surfaces 4| on one side of each of the hammers 39 will engage with the impact surfaces 30 on one side of each of the abutments 34 and 35 of the anvil 33. It is to be noted that the slightly curved extremities 40 of the hammers 39 do not engage with or slide in the walls of the anvil 33, but are always spaced slightly therefrom. The outward movement of the hammers 39 is limited by the pins 33, which engage with one of the curved extremities 40 of the undercuts 42. This, obviously, limits the outward movement of the hammers 39.

The aforesaid impacting surfaces remain in engagement, in a manner shown in Figure 2, until the nut is run down and the torque resistance to further rotation of the nut increases above a predetermined amount. When this occurs, the inclined surfaces 4! of the hammers 33 slide along similarly inclined surfaces 39 of the abutments 34 and 35 on the anvil 33. The hammer members 39, therefore, move inwardly to a position such as that shown in Figure 3. Obviously, the pins 33 limit the inward movement of the hammers 39 and prevent them from sliding through the holes 37 and 38. Shortly after the hammers 39 pass the abutments 33 and 35, they are again thrown outwardly by centrifugal force and continue in that position until they strike the next abutment during their rotational travel. This striking of the impact surfaces 39 and 4| delivers an impact blow to the anvil 33, which is transmitted through the extension 36 to the socket wrench 23. This imparts a strong impact blow to the nut and tightens it. As soon as the impact blow is struck, however, the hammers 39 will again be retracted, due to the shape of the impact surfaces 39 and M, the hammers 39 will slide past the abutments 34 and 35, centrifugal force will again throw the hammers outwardly and another impact blow will be delivered when the hammers 39 again strike the next abutments 3d and 35.

It will be apparent that, due to the offset position of the abutments 34 and 33 coaxially of the anvil 33, and because of the fact that the hammers 39 only extend outwardly of the carrier 2! in one direction thereof, the carrier 2'! will rotate a full 360 after each impact, before the next impact is delivered. The impact is then delivered simultaneously by the two hammers 39 striking the abutments 33 and 35 on the anvil 33. A rapid series of impact blows are, therefore, delivered to the nut, and it is thereby tightened.

The impact tool is adapted to be reversed, and for this reason, the impact surfaces 30 and 4| are provided on both sides of the abutments 34 and 35 and the hammers 39, respectively. Rotating the impact tool in the opposite direction makes it possible to loosen nuts which have already been tightened or to tighten nuts with left hand threads, as is well known in the art.

In operation, during the delivery of impact blows, the carrier 2? and the hammers 39 do not come to a full stop at any time. This is because of the fact that as soon as the impact surfaces 33 and 4H strike, the angle thereof immediately forces the hammers 39 inwardly and forward rotation continues.

Furthermore, it will be noted that there are no separate declutching means, such as springs or cams, for the hammers 39 and the abutments 33 and 33 on the anvil. Declutching of these parts is effected solely by the shape of the impact surfaces on the hammers and on the abutments on the anvil.

Description of Figures 9 and 10 Referring to Figures 9 and 10 for a detailed description of the second embodiment of the invention, like reference numerals have been given to like parts described in Figures 1 to 8, inclusive. The parts are substantially the same, except that a rectangular bore 52 is provided in the carrier member 2? instead of round holes 3'! and 38. Obviously, therefore, parallelepiped hammer members 53 are provided for insertion in the bore 52 instead of cylindrical hammer members.

Vertical surfaces of adjacent hammer members 53 slide on each other, as is apparent from'Figure 9. The hammer members are provided with inclined impact surfaces 54, which are adapted to engage with the impact surfaces 30 on the anvil 33. The anvil 33 is exactly as shown in Figures 1 to 8, inclusive, and the angles of the impact surfaces on both hammers and the anvil are the same. The hammer members 53 are provided with semi-elliptical undercuts 52 for the reception of two pins 55 which are inserted in bores 56 in the anvil member.

The operation of the impact tool shown in Figures 9 and 10 is the same as that described with respect to Figures 1 to 8, inclusive. Obviously, instead of rectangular blocks or parallelepipeds 53, hexagonal blocks may be utilized.

Description of Figures 11 and 12 Referring to Figures 11 and 12' for a detailed description of a third embodiment of the invention, again like numerals are given to like parts as utilized in the description of Figures 1 to 8, inclusive. In this embodiment of the invention, the carrier 21 is provided with a single rectangular bore 6!, in which hammers 62 are disposed. The hammers 62 are again rectangular blocks or parallelepipeds, but each of the hammers 62 has a projection 85 formed thereon adjacent the end of the hammer having impact surfaces 65 thereon adapted to engage with the impact receiving surfaces 39. The angles of the impact surfaces are the same as set forth with respect to Figures 1 to 8, inclusive. The projection 68 provides a fiat surface 63 and a fiat surface Gil at right angles to each other. The surfaces 63, when the hammers E32 are assembled, face each other, as best shown in Figure 11. The surfaces 64 slide on the flat vertical surface of the main portion of the parallelepiped hammers 62.

The hammers 62 are provided with an elliptical bore 66 centrally thereof, as best shown in Figure 12. .A single pin 6? is inserted in a bore 68 in the hammer carrier 2? and extends through the elliptical bores 66 of the hammerGZ.

The operation of the device shown in Figures 11 and L2 is the same as that described with respect to Figures 1 to 8, inclusive, except that the outward movement of the hammers 62 is limited by the pins El and elliptical bore 66 in each of the hammers 62. When the hammers are forced inwardly after an impact blow, the surfaces 63 thereof will engage and prevent further inward movement of the hammers. The elliptical bores 66 and the surfaces 63 are so proportioned that the bores 66 and pins 61 do not prevent or limit the inward movement of the hammers, but the surfaces 63 perform this function.

Description of Figures 13 and 14 Referring now to Figures 13 and 14 for a detailed description of the fourth embodiment of the invention, again like numerals are given to like parts. In this embodiment of the invention, two cylindrical bores 78 are provided in the carrier 21, but the bores are not cylindrical completely through the carrier 21'. Each of the bores extends in cylindrical form part Way through the carrier 2? and then is provided with an inwardly tapered surface H and a reduced cylindrical bore 718. A pair of generally cylindrical hammers i having impacting surfaces 12 thereon, are positioned within the bores it. The impacting surfaces 12 are adapted to. engage with m te .. the. impact receiving surfaces 3 0. .The angles of the'impact surfaces are the same asset forth with respect to Figuresl to 8, inclusive. The inner ends of the hammers H are provided with tapered ends it which conform with the configuration of the tapered portion H of the bores 1B.

, Each of the hammers 1| is provided with semi- I elliptical undercuts 13 similar in shape to those tapered portion it of the hammer striking or engaging with the tapered portion H of the bores iii. In other words, the pins 14 perform no function in limiting the inward movement of the hammers. The recess 13, the tapered portions 16 of the hammers and the tapered portions 11 of the bores l!) are so proportioned, however, that the pins 74 limit outward movement of the hammers H in the same manner as described with respect to Figures 1 to 8, inclusive. As stated above, however, the pins I4 have nothing to do with preventing inward movement of the hammers. The reduced bores 18 provide for release of air below the hammers H, so that in this embodiment of the invention, very little, if any,

' cushioning effect, because of entrapped air, is

- present.

Description of Figures 15 and 16 Referring now to Figures 15 and 16 for a detailed description of a fifth embodiment of the invention, again like'reference numerals are given hammer members 8!, having impact surfaces 82,

are provided, which cylindrical hammers 8| are formed with semi-elliptical undercuts 83 similar in shape to those disclosed, for example, in Figure 3. The impact surfaces .82 are adapted to engage .with the impact surfaces 30, and the angle of the impact surfaces is the same as set forth with respect to Figures 1 to 8, inclusive. Two pins as are inserted in coaxially extending bores 85 in the hammer member 2?, which pins are received in the semi-elliptical recess 83, in a manner shown in Figure 16.

The ends of the hammers 8| opposite to the impact surfaces 82 are preferably flat and are I adapted to engage or strike against the flat surface of the abutment of the bores 89. The operation of the device is exactly the same as described with respect to the device shown in Figures 13 and 14, except that air may escape from below the hammers 8! only along the sides thereof and, therefore, a slight cushioning effect is provided.

Obviously, the shape of the hammer elements and the bores for receiving them may be varied considerably, depending on the type of machining operation desired. I have provided an efii cient impact tool which is reversible and which I tion and arrangement of the parts ofv my device directions to force said hammers inwardly of said carrier upon a predetermined increase in the resistance to torque of said tool, and means independent of the anvil for limiting both the inward and outward movement of said hammers.

6. An impact tool comprising a driven member adapted to be rotated continuously, a hammer carrier, means for rotating said hammer carrier with said driven member, a pair of axially alined and axially spaced non-rotatable hammers movable transversely to the axis of said hammer carrier and carried thereby, impact surfaces adjacent the outer end of each of said hammers, said impact surfaces being the same surfaces at all times due to the non-rotating nature of the hammers, said hammers being positioned in said carrier with said impact surface ends extending in different directions, said hammers moving outwardly with respect to said hammer carrier in response to centrifugal force when said hammer carrier is rotated, an anvil member encompassing a portion of said hammer carrier and having substantially flat impact receiving surfaces thereon disposed in the path of the impact surfaces of said hammers when said hammers are moved outwardly by centrifugal force and a tool secured to said anvil and driven thereby, said impact surfaces on said anvil being axially spaced and so arranged that an impact blow is delivered thereto every 360 rotation of said individual hammers.

'7. An impact tool comprising a driven member adapted to be rotated continuously, a hammer carrier, means for rotating said hammer carrier with said driven member, a pair of axially spaced non-rotatable hammers movable transversely to the axis of said hammer carrier and carried thereby, impact surfaces adjacent the outer end of each of said hammers, said impact surfaces being the same surfaces at all times due to the non-rotating nature of the hammers, said hammers being positioned in said carrier with said impact surface ends extending in different directions, said hammers moving outwardly with respect to said hammer carrier in response to centrifugal force when said hammer carrier is rotated, an anvil encompassing a portion of said hammer carrier and having substantially flat impact receiving surfaces thereon disposed in the path of the impact surfaces of said hammers when said hammers are moved outwardly by centrifugal force, a tool secured to said anvil and driven thereby, said impact surfaces on the hammers and impact receiving surfaces on the anvil being tapered in opposite directions to force said hammers inwardly of said carrier upon a predetermined increase in the resistance to torque of said tool and means independent of the anvil for limiting the outward movement of said hammers, said impact surfaces on said anvil being axially spaced and so arranged that an impact blow is delivered thereto every 360 rotation of said individual hammers.

EDGAR R. WHITLEDGE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,373,664 Emery Apr. 17, 1945 2,425,793 Fosnot Aug. 19, 1947 2,439,337 Forse Apr. 6, 1948 2,508,997 Fitch May 23, 1950 2,575,523 Mitchell Nov. 20, 1951 

